1. Field of the Invention
The present invention relates to an audio system including a disc reproduction device, such as a DVD player, capable of sending/receiving an audio signal via an IEEE 1394 interface, and an AV (Audio Video) amplifier for amplifying the audio signal from the disc reproduction device to output the amplified audio signal to a speaker.
2. Description of the Related Art
Audio systems well known in the art include those whose components, i.e., an AV amplifier and a disc reproduction device, are connected together via an IEEE 1394 interface, and those in which two or more speaker systems installed in different rooms are connected to an AV amplifier so that the user can enjoy music in any of these rooms. These audio systems can be found in, for example, Japanese Laid-Open Patent Publication Nos. 11-355326 and 2003-259467.
A player is a sound source-side component of an audio system. A conventional player is capable of reading recorded data (digital audio data) from different types of discs, such as a DVD (Digital Versatile Disc), a CD (Compact Disc) and an SACD (Super Audio CD), and includes a digital output path in which the read digital data is output as it is from a digital output terminal, an analog output path in which the read digital data is converted into an analog signal and output from an analog output terminal, and an IEEE 1394 output path in which the read digital data is converted into data to be transferred in compliance with the IEEE 1394 standard (hereinafter referred to as “IEEE 1394 data”), which is output from an IEEE 1394 interface.
Specifically, a player of this type includes a disc reading section for reading recorded data from a disc, a DSP (Digital Signal Processor) for converting the read data into an analog signal, a DSD decoder for decoding DSD (Direct Stream Digital) audio data read from an SACD, and an IEEE 1394 selector for selecting whether or not to output the read data (decoded data from the DSD decoder in the case of SACD) through the IEEE 1394 interface.
In the digital output path, data read from the disc is output as it is from the digital output terminal. In the analog output path, data read from a non-SACD disc is output from the analog output terminal via the DSP, and data read from an SACD is output from the analog output terminal via the DSD decoder and the IEEE 1394 selector if the IEEE 1394 selector is in such a setting that data is not output from the IEEE 1394 interface. In the IEEE 1394 output path, data read from the disc is output from the IEEE 1394 interface via the DSD decoder and the IEEE 1394 selector if the IEEE 1394 selector is in such a setting that data is output from the IEEE 1394 interface.
The setting of the IEEE 1394 selector can be changed by the user operating a control section. In the “IEEE 1394 ON” setting, data read from the disc is output from the IEEE 1394 interface. In the “IEEE 1394 OFF” setting, data read from the disc is not output from the IEEE 1394 interface.
Table 1 below shows whether an audio signal can be reproduced for each combination of the IEEE 1394 selector setting in the player, the disc type and the type of output terminal. As can be seen from Table 1, where an SACD is loaded in the player, the audio output cannot be obtained unless the subsequent AV amplifier receives digital audio data via the IEEE 1394 interface if the IEEE 1394 selector is in the “IEEE 1394 ON” setting, and audio output cannot be obtained unless the AV amplifier receives an analog signal via the analog input terminal if the IEEE 1394 selector is in the “IEEE 1394 OFF” setting.
TABLE 1IEEE 1394 selectorOutputIEEE 1394 ONIEEE 1394 OFFTerminalCDDVDSACDCDDVDSACDAnalogplayableplayableunplayableplayableplayableplayableDigitalplayableplayableunplayableplayableplayableunplayableIEEEplayableplayableplayableplayableplayableunplayable1394
A speaker is an output-side component of an audio system. A conventional speaker system includes a plurality of speakers of different frequency bands for compatibility with a surround system (e.g., six speakers are included in a typical 5.1-channel surround system).
An AV amplifier is an intermediate component provided between the player and the speaker. A conventional AV amplifier offers a connectability such that a plurality of players as described above and a plurality of speaker systems as described above can be connected to the AV amplifier. Specifically, such an AV amplifier includes a group of input terminals (including a plurality of digital input terminals, a plurality of analog input terminals, and an IEEE 1394 interface), a group of output terminals (including a plurality of sets of multi-channel speaker output terminals), and an audio signal processing section. The audio signal processing section selects a signal path between an input terminal of the group of input terminals and a multi-channel speaker output terminal of the group of output terminals. The audio signal processing section also performs predetermined signal processing operations, such as converting digital audio data into an analog audio signal, and amplifying a signal level.
For example, a conventional AV amplifier includes two sets of multi-channel speaker output terminals, a first audio signal processing section for a first set of multi-channel speaker output terminals, and a second audio signal processing section for a second set of multi-channel speaker output terminals. The first audio signal processing section can selectively output digital audio data or an analog audio signal received from a digital input terminal, an analog input terminal or an IEEE 1394 interface to the first set of multi-channel speaker output terminals (the output system for a signal passing through the first audio signal processing section will hereinafter be referred to as the “first speaker output system”). The second audio signal processing section can selectively output digital audio data or an analog audio signal received from a digital input terminal or an analog input terminal to the second set of multi-channel speaker output terminals (the output system for a signal passing through the second audio signal processing section will hereinafter be referred to as the “second speaker output system”).
An AV amplifier of this type includes an IEEE 1394 selector similar to that provided in a player. Moreover, the first audio signal processing section is provided with a first input selector for selecting digital audio data or an analog audio signal from a digital input terminal, an analog input terminal or an IEEE 1394 interface, and the second audio signal processing section includes a second input selector for selecting digital audio data or an analog audio signal from a digital input terminal or an analog input terminal. These input selectors can be switched by the user operating a control section.
For example, where two players as described above are connected as sound sources to such an AV amplifier, the user can control the first and second input selectors so that the audio output from one player is simultaneously output from two speaker systems installed in two different rooms via the first and second speaker output systems, or so that the audio output from one player is output from one speaker system via the first speaker output system while the audio output from the other player is output from the other speaker system via the second speaker output system.
In the audio system described above including two players, an AV amplifier and two speaker systems, the first speaker output system receives digital audio data input from the IEEE 1394 interface, but the second speaker output system does not receive digital audio data input from the IEEE 1394 interface. Thus, the digital audio data cannot be reproduced through the second speaker output system. For example, where reproduced sound signals from different players are output from different speaker systems, the following problem arises. If the IEEE 1394 selector of the player being the sound source for the second speaker output system is set to “IEEE 1394 ON” and if an SACD is loaded in the player, a sound signal reproduced from the SACD cannot be output from the speaker system via the second speaker output system, as shown in Table 2 below.
TABLE 2Input typeFirst speaker output systemSecond speaker output systemAnalogplayableplayableDigitalplayableplayableIEEE 1394playableunplayable
Similarly, where a sound signal reproduced from the same player is output from the two speaker systems, if the IEEE 1394 selector of the player being the sound source for the first and second speaker output systems is set to “IEEE 1394 ON” and if an SACD is loaded in the player, the reproduced sound signal cannot be output from the speaker system connected to the second speaker output system.
FIG. 4 is a block diagram showing a basic configuration of an audio system for illustrating this problem in a generalized form.
With the configuration shown in FIG. 4, two players 500A and 500B can simultaneously output audio signals each in any of three different signal formats. However, for a special type of a disc such as an SACD, only a signal format A or B can be selected by a selector 501. An AV amplifier 600 includes a first audio output processing section 601 and a second audio output processing section 603. The first audio output processing section 601 can output, to a first speaker system 701, an audio signal selected by a first input selector 602 from among audio signals of three signals formats A, B and C received from each of the players 500A and 500B. The second audio output processing section 603 can output, to a second speaker system 702, an audio signal selected by a second input selector 604 from among audio signals of two signal formats B and C received from each of the players 500A and 500B.
The first audio output processing section 601 of the AV amplifier 600 is connected only to the first speaker system 701, and the second audio output processing section 603 thereof is connected only to the second speaker system 702. Thus, the first input selector 602 selects the sound source for the first speaker system 701, and the second input selector 604 selects the sound source for the second speaker system 702.
The first input selector 602 receives a total of six audio signals, i.e., audio signals A1, B1 and C1 from output terminals 502, 503 and 504 of the player 500A and audio signals A2, B2 and C2 from output terminals 502, 503 and 504 of the player 500B. The second input selector 604 receives a total of four audio signals, i.e., audio signals B1 and C1 from the output terminals 503 and 504 of the player 500A and audio signals B2 and C2 from the output terminals 503 and 504 of the player 500B. Therefore, unless a special type of a disc is loaded in the player 500A or 500B, the player 500A can be selected as the sound source for the first speaker system 701 while selecting the player 500B as the sound source for the second speaker system 702, and vice versa.
However, if a special type of a disc is loaded in either or both of the players 500A and 500B, the user may not be able to select a particular combination or particular combinations between the players 500A and 500B and the first and second speaker systems 701 and 702.
For example, where a special type of a disc is loaded only in the player 500A, if the selector 501 of the player 500A is set to the signal format B and if the first input selector 602 of the AV amplifier 600 selects the audio signal A1, as shown in FIG. 5, an audio signal from the player 500A cannot be output from the first speaker system 701.
Where discs of a special type are loaded in the players 500A and 500B, if the selectors 501 of the players 500A and 500B are both set to the signal format A and if the first input selector 602 of the AV amplifier 600 selects the audio signal A1 while the second input selector 604 selects the audio signal B2, as shown in FIG. 6, an audio signal from the player 500A can be output from the first speaker system 701 but an audio signal from the player 500B cannot be output from the second speaker system 702.
The first input selector 602 and the second input selector 604 of the AV amplifier 600 are used by the user selecting the sound sources to be reproduced through the first speaker system 701 and the second speaker system 702, respectively. Therefore, it is preferred that the first input selector 602 (or the second input selector 604) receives a type of an audio signal intended by the user according to the setting of the selector. However, in cases shown in FIG. 5 and FIG. 6, the type of an audio signal intended by the user is not provided from a player, and the user needs to change the setting of the selector 501 of the player 500A or 500B to the intended signal format.
Specifically, in the case of FIG. 5, the user needs to change the setting of the selector 501 so that the audio signal A1 is output from the player 500A, and in the case of FIG. 6, the user needs to change the setting of the selector 501 so that the audio signal B2 is output from the player 500B.
With an audio system using an AV amplifier as described above, each time the user places a disc in the player 500A or 500B, the user needs to select the output audio signal format of the player 500A or 500B so that it matches with the input audio signal format required by the first or second audio output processing section 601 or 603 of the AV amplifier 600 corresponding to the player 500A or 500B. This can be tiresome for the user.
This problem can be avoided if the first audio output processing section 601 and the second audio output processing section 603 of the AV amplifier 600 have the same configuration, and the AV amplifier 600 can select any of a total of six audio signal formats from the players 500A and 500B for each of the first and second audio output processing sections 601 and 603. However, it is typical for a user to have main and sub-speaker output systems to keep the AV amplifier 600 simple and inexpensive while obtaining a high functionality, e.g., by using the first audio output processing section 601 and the first input selector 602 as the main speaker output system and the second audio output processing section 603 and the second input selector 604 as the sub-speaker output system. Then, the problem above is inevitable.